Typical information or data processing systems or electronic systems include various subsystems or modules. The subsystems or modules may provide various functionality. The modular nature of the system (e.g., using subsystems) affords system designers more flexibility in designing and producing the system.
By their nature, systems typically include apparatus for two or more of the subsystems or modules to communicate together. The communication may occur over buses. One example of such a bus constitutes USB, a ubiquitous serial bus that provides communication between various modules, subsystems, or circuitry in electronic systems, such as data-processing systems, computers, etc.
Since the introduction of USB, a variety of refinements and improvements have been made. An example constitutes U.S. Pat. No. 6,917,658, which discloses a clock recovery method that allows a USB device to operate using an internal oscillator rather than a crystal oscillator (or an internal oscillator frequency locked to a crystal clock).